Sensitive oscillators could lead to detection of harmful molecules, bacteria

By watching how energy moves across a tiny device akin to a springing diving board, Cornell researchers are a step closer to creating extraordinarily tiny sensors that can instantly recognize harmful substances in air or water.

The researchers, led by professor of applied and engineering physics Harold Craighead, made a device just 200 nanometers thick and a few microns long with an oscillating cantilever hanging off one end. (A nanometer is one-billionth of a meter; a micron is one-millionth of a meter.) They identified exactly how to tune its sensitivity -- a breakthrough that could lead to advanced sensing technologies.

The experiments detailed online Feb. 8 in Journal of Applied Physics show how these oscillators, which are nanoelectromechanical systems (NEMS), could one day be made into everyday devices by lining up millions of them and treating each cantilever with a certain molecule.

"The big purpose is to be able to drive arrays of these things all in direct synchrony," said first author Rob Ilic, a research associate at the Cornell NanoScale Science and Technology Facility. "They can be functionalized with different chemistries and biomolecules to detect various pathogens -- not just one thing."

The cantilever is like a diving board that resonates at distinct frequencies. In past research, the team has demonstrated that by treating the cantilever with different substances, they can tell what other substances are present. For example, E. coli antibodies attached to the cantilever can detect the presence of E. coli in water.